Various methods of countercurrent chromatography have been proposed, for example, methods as disclosed in the article by Ito and Bowman in "Journal of Chromatographic Science", Vol. 8, pp 315-323, June 1970. These methods include helix countercurrent chromatography, droplet countercurrent chromatography, and rotational and gyratory-movement countercurrent chromatography.
The theoretical considerations involved in helix countercurrent chromatography have been pointed out in detail in U.S. Pat. No. 3,775,309, to Ito and Bowman, and in an article by Ito, et al., in "Analytical Chemistry", Vol 41, pp. 1579-1584, October 1969, cited in said U.S. patent. It was noted in said patent that flow became difficult because of the need for rotating seals, and because of this, flow-through operation was somewhat impractical and that the practical use of the method was limited by problems of sample introduction and fractionation.
A preliminary search of the prior art revealed the following prior U.S. patents, which appear to indicate the present state of the art:
Ito, U.S. Pat. No. 3,775,309 PA1 Ito, U.S. Pat. No. 3,856,669 PA1 Khoja, et al., U.S. Pat. No. 3,986,442